Institutional mattress



FIG. 1 illustrates a top perspective view of the institutional mattress;

FIG. 2 illustrates a top view of the mattress;

FIG. 3 illustrates a bottom view of the mattress;

FIG. 4 illustrates a side view of the mattress, the opposite side being a mirror image; and,

FIG. 5 illustrates a foot end view of the mattress.

The broken lines are for environmental purposes only and form no part of the claimed design. 

The ornamental design for an institutional mattress, as shown and described. 